Introduction Pneumonectomy results in impairments of pulmonary function and exercise intolerance associated with respiratory limitations. However, exercise capacity and functional capacity are less known at long-term followup. The aims of this study were to assess exercise tolerance and functional capacity among long-term postpneumonectomy patients and to identify the limiting factors in exercise related to comorbidities and which lung was involved. Methods Seventeen postpneumonectomy patients aged 59 ± 13 years and 5.5 ± 4.2 years postoperation were prospectively studied. Pulmonary function tests (PFTs), cardiopulmonary exercise test (CPET), Doppler-echocardiography, 6-minute walk test (6MWT) distance, and "senior fitness tests" (SFTs) were conducted with all patients. Results Exercise capacity and PFT were diminished ((Equation is included in full-text article.)O2 peak; 11.5 ± 3.3 mL·kg·min, 48 ± 17% predicted, forced vital capacity % predicted; 55 ± 13, FEV1% predicted; 46 ± 14, respectively). Most patients presented with low exercise cardiovascular parameters and normal breathing reserve (17 ± 12 L) during CPET. No significant differences were shown between right and left pneumonectomy and comorbidities related to exercise limitations (χ= 1.96, P = .376). Functional capacity in walking and SFTs were near normal (6MWT distance; 490 ± 15 m, 89 ± 25% predicted). Echocardiography showed normal left ventricle systolic function (ejection fraction, 60 ± 4%) with mildly elevated systolic pulmonary arterial pressure (38 ± 12 mm Hg). Conclusions Long-term postpneumonectomy patients demonstrated decreased exercise capacity, limited primarily by the cardiovascular system regardless of lung resection side or comorbidities, although tests of functional capacity were near normal. Most patients can maintain near normal life in activities of daily living, but the long-term cardiopulmonary exercise function should be considered for meticulous evaluation and clinical care to preserve physiological reserves.